By Nick Assinder
Political Correspondent, BBC News website
Britain's political parties are presenting a united front over the London bombings, aware that any sign of division will offer the terrorists a cause for celebration.
But this political unity has already come under pressure as the Conservatives demanded an inquiry into the attacks, some MPs claimed the Iraq war was a contributory factor, and concerns over possible new laws were raised.
Blair believes inquiry unhelpful
And, as the initial shock and anger begins to subside, there is the real possibility these strains will intensify.
Home Office minister Hazel Blears betrayed the government's irritation, even anger, at the Tory demands for an inquiry.
And the private message from Downing Street was that the call was irresponsible as an inquiry would distract the police and security services from the job in hand of hunting down the killers.
Senior Tories clearly recognised the dangers and, when it came to the Commons statement, Michael Howard significantly softened his line.
Until now, the Tories - and in particular leadership favourite, David Davis - had attracted praise for the way they responded to the atrocity.
But there was a clear danger for the opposition that the call for an inquiry might appear to be undermining that cross party unity and paint them as opportunistic, even insensitive.
So when it came to responding to the prime minister in the Commons, Mr Howard backed away from demanding an immediate inquiry in favour of suggesting a future probe to learn any lessons.
Davis offered support
And he accompanied it with a glowing tribute to the prime minister's "resolute and statesmanlike" leadership - a sentiment echoed across the chamber.
Meanwhile, there has been an angry reaction to Respect MP George Galloway's suggestion London paid the price for the war on Iraq.
Yet he is far from a lone voice in believing the war, and Britain's support for the US, increased the possibility of an attack on Britain.
Labour MPs including former defence minister Peter Kilfoyle and Merseyside's Bob Wareing have both stated they believe Tony Blair's support for the US and the war on Iraq made Britain a target.
Indeed, it has been pointed out that the Butler inquiry revealed that the joint intelligence committee stated before the war that military action against Iraq action might "heighten", rather than reduce, the terrorist threat to western interests.
The prime minister is quick to counter that 11 September happened before the invasion of Iraq and that there is no link between the war and the attacks on London.
That is a statement that has been backed by Liberal Democrat leader Charles Kennedy, who consistently opposed the war.
Iraq war not to blame says Blair
But Mr Kennedy has gone on to voice other concerns in the Commons over the possible government reaction to the attacks, demanding that civil liberties are not cast aside in any move to introduce new anti-terror laws.
That has been encouraged by Home Secretary Charles Clarke's statement that ID cards would not have prevented the attacks.
These are all arguments that many in Westminster are still reluctant to get into for fear of sparking claims they are encouraging division at a time that demands unity.
But, while the Tories may soften their demands for an inquiry, there is still the real likelihood the unity will come under severe strain in coming weeks and months.
What all are agreed on, however, is that they should not get in the way of, but rather aid, a coherent and proportionate response to the attacks.